Steel is usually refined in a vessel called a crucible in which it is held in a liquid state while the composition of the steel is corrected. The top of the steel melt in the ladle is covered with a layer of slag. The ladle is lined with a refractory lining that prevents the molten steel from coming in contact with the steel shell of the crucible and which takes part in the refining operation. The principal obstacle to operating the same ladle continuously for, for example, several days is the wear of this refractory lining since, once the lining is reduced in thickness it must be renewed to prevent the steel melt from coming into direct contact with the metal shell. The refractory lining wears principally in regions in which it comes into contact with the slag on top of the melt, the remainder of the refractory lining having a much longer service life.
It has been suggested to increase the service life of these refractory linings by periodically locally renewing them in the regions of greatest wear. This is carried out by spraying or projecting refractory material in the worn spots and allowing it to harden. Such operations require that a complete halt be made to the refining operation and that the ladle in question be emptied completely for it to be carried out.
It has also been suggested to include in the refining slag, limestone and dolomite so as to saturate the slag in magnesium oxide and thereby considerably reduce its corrosivity. In practice the pulverized dolomite is added to the limestone blown by lances into the melt. According to this process the corrosivity of the slag is reduced considerably, however the refractory lining still wears considerably more in the region of the slag than elsewhere so that it must be renewed at this location when the remainder of the refractory lining is still in excellent condition.